This invention relates broadly to the field of systems and methods for metering the flow of a first liquid into the flow of a second liquid. More particularly, it relates to a system, including a novel metering valve, for metering the flow of a fuel additive into the flow of fuel into a fuel tank.
Concerns for increased fuel economy and reduced exhaust emissions have led to an increased demand for motor vehicle fuel additives that achieve one or both of these ends. In the past, such additives were simply poured into the fuel tank of the vehicle during refueling, with little concern for precise proportions of additive and fuel.
Recent advancements in fuel additive technology have led to new fuel additives that provide significantly improved mileage and emissions control, but which require fairly precise proportions of the fuel and additive mixture for cost effectiveness. Thus, if the additive-to-fuel ratio is too low, the benefits of the additive are not fully realized; if the ratio is too high, the excessive additive provides no additional benefit, and is, therefore, wasted. One particular fuel additive of this type that has recently been developed for gasoline and diesel engines is marketed by Wynn's International, Inc., of Fullerton, Calif., under the trademark "EMISSION CONTROL". Such a product is described in U.S Pat. No. 4,684,373.
It will readily be appreciated that pouring a container of such an additive into the fuel tank during refueling cannot provide any meaningful control over the additive-to-fuel ratio, unless the additive is added only when the tank is substantially empty. Such a regimen is impractical, for obvious reasons, when dealing with motor vehicles.
Accordingly, a mechanism is needed to mix the additive into the fuel so as to achieve and maintain the proper additive-to-fuel ratio, regardless of the amount of fuel in the fuel tank.
The problem of metering an additive liquid into a principal liquid so as to achieve and maintain a constant proportion between the two liquids has been addressed in a number of ways in the prior art. For example, this problem has arisen in the context of adding motor oil to gasoline in a two-stroke internal combustion engine. U. S. Pat. No. 4,069,835 to Stadler illustrates one approach to this specific problem. The Stadler reference discloses a device that attaches to a fuel tank, and that comprises an oil container with a piston valve at the bottom. The valve is operatively connected to a lever in a fuel inlet conduit situated adjacent to the oil container. The flow of fuel through the conduit pivots the lever, thereby opening the valve to allow oil to flow, by gravity, into a mixing chamber to mix with the fuel that has passed through the conduit. The valve is operated so that the flow rate of the oil is proportional to the flow rate of the fuel. U.S. Pat. No. 2,935,057 to Perlewitz discloses a device that uses pressure from the crankcase of the engine to force oil and fuel to flow from separate chambers into a mixing chamber, the proportion of oil to fuel being set by the relative diameters of the conduits that conduct the oil and fuel, respectively, into the mixing chamber.
Neither of the above-described devices is readily adjustable to accommodate additives of differing viscosities. Moreover, the Stadler device requires installation and removal during each refueling operation, while the Perlewitz device requires some engine modification, and is, therefore, not well-suited for use as an add-on accessory for existing engines.
Another approach is exemplified in U.S. Pat. No. 4,714,087 to Jones, which discloses an apparatus that uses pressurized fuel oil, from the high pressure, downstream side of a fuel pump, to aspirate an additive into the fuel oil supply conduit on the upstream side of the pump. This apparatus is specifically adapted for the delivery of additive-enhance heating fuel from a supply truck to a stationary storage tank. U.S. Pat. No. 2,826,211 to Reed discloses a system for injecting an additive into a fuel stream while the fuel is flowing from one receptacle to another. The Reed system is a fixed installation, not adaptable to installation on board a motor vehicle. It can be appreciated that the prior art has not adequately addressed the need for a system, easily installed in an existing motor vehicle, that allows an additive to be mixed with fuel in precise and repeatable proportions, regardless of how much fuel is in the fuel tank of the vehicle. Such a system must be able to accommodate additives of different viscosities, and it must allow the mixing hardware, as well as the additive supply, to be carried on the vehicle, so that the vehicle is not dependent upon the existence of either an additive supply or the mixing hardware at each filling station. Such a system should also be quick and easy to use, with a minimum of skill on the part of the operator. Finally, such a system should be economical to manufacture, install, and use, and yet be sufficiently rugged and durable to withstand long-term use in a motor vehicle.